Plural evaporator reversal control mechanism



June 11, 1957 e. MUFFLY PLURAL EVAPORATOR REVERSAL CONTROL MECHANISMFiled Sept. 4, 1951 2 Shets-Shee'c l NW vmum wh m IN V EN TOR. Gi /W1Muff/g, BY

June 11, 1957 G. MUFFLY 2,795,112

PLURAL EVAPORATOR REVERSAL. CONTROL MECHANISM Filed Sept. 4, 1951 2Sheets-Sheet 2 United States Patent PLURAL EVAPORATOR REVERSAL CONTROLMECHANISM Glenn Mufliy, Springfield, Ohio Application September 4,1951,Serial No. 244,964

Claims. (Cl. 62- 3) This invention has to do with valves for the controlof refrigerant flow, particularly in ice-making systems and airconditioning systems of the reversible heat pump type. it includesimprovements over my U. S. Patent No. 2,497,903, issued February 21,1950; my copending U. S. application Serial Number 45,343, filed August20, 1948, now Patent No. 2,654,227; my copending -U. S. applicationSerial Number 50,101, filed September 20, 1948, now Patent No.2,672,016; my copending U. S. application Serial Number 174,944, filedJuly 20, 1950, now Patent No. 2,774,223. The drawings and specificationare in the main duplications of a part of'my Canadian patent applicationSerial Number 618,079, filed July 14, 1951.

It is an object of this invention to provide a valve mechanism actuatedby refrigerant l'low which not only produces the desired periodicreversals of flow, but also causes cessation of liquid how to providethe desired pumping-out periods.

Another object is to provide a readily accessible adjustment for varyingthe length ofice-making periods, thus modifying the diameter of the icedisks or causing ice to be released before the two opposed thin disks ofie join to form a thicker disk.

An additional object is to provide a suction vapor control valve havingno outside connection with a control device and being actuatedautomatically in response to the shifting of liquid refrigerant flow andto changes in the relative vapor pressures within an evaporator whichhas just finished itsdefrosting' or ice-releasing period and the activesuction pressure of the system.

A still further object is to provide a system in which two or moreevaporators are active in freezing ice while a lesser number ofevaporators are being heated by the specific heat'of liquid refrigerantflowing to the active evaporators,'thus causing each evaporator to beactive a greater percentage of the time.

Another object is to provide a control system suitable for use inshifting or reversing flow of refrigerant in various types ofrefrigerating or heat-pump apparatus.

In the drawings:

Figure 1 is a sectional view of a valve mechanism actuated byrefrigerant vapor flow and designed to control both liquid and vapor.

Figure 2 is a fractional sectional view of Fig. 1 on the line 2-2thereof.

Figure 3 is a sectional view of a rotary valve designed to be actuatedby the pinwheel and gear train of Fig. 1.

Figure 4 is a sectional view of a magnetically actuated valve mechanismwhich may be used in place of the valve assembly seen in Fig. 1.

Figure 5 is a detail sectional view of Fig. 4 on the line 5-5 thereof.

Figure 6 is a sectional view of a solenoid valve having two outlets andusable in Fig. 4 to replace the upper valve assembly thereof. 7

Figure 7 is a sectional view of an assembly of two soleposition as inFig. 1, which means that the rocker 364 3 2,795,112 Patented June 111957 s 2 mid valves which may replace the two upper "valves of Fig. 4.

Figure 8 is a diagrammatic viewo'f'a'n ice-making s'ys' tem'employingthree or more evaporators, showing a'suit able arrangement of tubingan'dcontrol valves. a Figure 9is a detail sectional 'view ofjFig. 8 onthe-line 9-9 thereof, showing a modificationof the valyesofFi'g. 4 foruse when ice istobe frozenby two or more eva'pora' tors at a time, as ina machine oflarger'capacity. 5 All of these figures show valvecontroldevicesadapted for use in connection with ice-making systems such'asshown in my previous U. S. Patents and applications above mentioned.Typical refrigerant circuits for such systems are shown in Figs. 1,2-and 8 of this'applicat-ioh. Figure 1 shows a valve assembly adaptedforu'se in a system such as is shown by Fig. 4 of my cop'endingUJ'S.application Serial Number 174,944 replacing valves '72, 84, -86 and 88thereof and obtaining energy 'for' thir operation from refrigerant vaporflow on the 'orde'rdf my United States Patent' 2,497,903but-controllingliquid-as well as vapor and providing the pump out"peritid.

InFigure 1 the low pressurerefrigerant vaporflowing from the activeevaporator enters'the valve assembly31'0 through the tube 270. It entersthe chamber 314 and flows'therefrom through the port 316 whichis nowopnbut will later be closed by means of the valve'31'8. he refrigerantvapor is free to flow withinthe chamber 320 and thence through the ports322 whichare' so' positioned that the flow of refrigerant vapor drivesthepinwheel 324 as the vaporenters the chamber 32 6 fro'm=whiehit flowsthrough the outlet port 328 were s'uctiontube '274 which leads to thecompressor 275, which dischar ge's in to the'condenser 277. l

The pinwheel 324 is attached to the hollow stub shaft 334 carryingpinion 336 which drives'the gear 338; has'a pinion 340*serving as itshub and rotating freely upon the shaft 342. The'pinion 340 drives thegear 338' whichis similar to the gear 338 and has attached thereto asimilar pinion 340 whichrotates 'freely'upon the shaft 344. Several suchassemblies of a gear and a pinion r tating together freely on one or theother of the two shafts provide a great'r'eduction in gear speed untilfinally the driven gear 346 rotates 'atsay one'revolu'tioniperihourwhereas the pinwheel 3'24 and its connected pinionff336 revolve at say,1,000 R. P. M. The drivenigear346, unlike the other driven gears, iskeyed to the 'shaft 342 or to a tubular extension of'the cam 348 sothat'the cam is driven at the same speed as the gear 346. In case thegear 346 is keyed to the shaft 342 the cam 348' is'als'o keyed to theshaft 342. Mounted on the cam is acra'nlc pin 350 (Fig. 2) which may beprovided'with roller 352. This roller fits freely within the slot 354 ofthe Ul-sha'p'ed lever 356 which carries one end of the spring358. "Thisslot need'not be straight as shown. It mayhavecurved sidesand be widenedat the bottom to compensate for any inequalities in the rate of levermovemenfrelative to cam rotation, but'this is not necessarysincethefportant timing occurs when the crank pin 350- and the point 360 of thecam are in approximately the same horizontal plane as the shaft 342.With the exceptionof the pinwheel 324 which rotates with the pinion 336andof the gear'346, which carries'the cam 348,-each gear 338' is' fixedto a pinion 340 and rotates freelyon its sha'ft;

Figure 2 shows the rocker-362 in the same horizontal (Fig. 1) occupies asimilar position in which neither the liquid valve 366 nor its similarmating valve' 367, a"c tuated by the opposite end of the rocker"364, is"from its seat. Since high pressure liquid refrigerant enters the chamber368 through the tube" 2 82"' the"pres- 3 1 sure within the chamber 368aids gravity in holding the valves 366 and 367 closed... l

In the position shown in Fig. .2, the cam 348 is rotating to the rightand has almost reached the position at which the point 372 of the rocker362 will fall off the point 360 of the cam. As point 372 is released therocker362 will move clockwise upon the shaft 374 due to the tension ofspring 358 which is connected with the downwardly extending arm 376 ofthe rocker 362. This clockwise movement of the rocker 362 causes theclosing of the valve 318 and the positive opening of valve 378 in casethe latter has not already been opened by gravity due to the pressureswithin the two evaporators and their connected chambers 314 and 380becoming substantially equalized. It will be noted that when the rocker362 tilts clockwise in Fig. 2 the rocker 364 (Fig. 1) moves with itbecause bothare keyed to the shaft 374. The

movement of rocker 364 lifts the liquid valve 366 from its seat,allowing high pressure liquid refrigerant to flow through the tube 270tothe inactive evaporator while the corresponding valve 367 remainsseated to prevent the flow of liquid through the tube 285 to theevaporator 214 which is now connected with the chamber 380 of the opensuction valve 378.

It will be noted thatwhen the rockers 362 and 364 are in theirhorizontal position all four of the valves 366, 367, 318 and 378 arefree to open or close under the influence of fluid pressure differencesacross them. Since there is always high pressure liquid in the chamber368 the valves 366 and 367 remain closed. The valve 378 remains closedas indicated in Fig. 2 until the pressure in chamber 380 falls to nearlythe operating suction pressure, at which time gravity causes the valve378 to open.

It is thus seen that refrigeration of one evaporator will continue andthe other evaporator will be flooded with warm high pressure liquidrefrigerant until the cam has rotated say 150 thus causing the lever 356to swing to the right to a position at which the spring 358 will causethe rocker 362 to snap to the left. Since the point 360 of the cam nowengages the point 384 of the rocker 362 the rock er iststopped atapproximately its horizontal position as seen in Fig. 2 but the springisurging it counterclockwise and after the cam has rotated about 30 moreto the right to complete a half revolution the point 384 will fall offof the cam point 360. and the rocker will. continueits movement to theleft thus closing the suction valve 378 and opening the liquid valve 367to cause hot high pressure liquid refrigerant to flow through thechamber 380 and the tube 285 to the evaporator 214 while vapor iswithdrawn from the now active evaporator 216.. These cycles as describedwill continue with substantially constant periods of ice-making, thawingoff with hot liquid and pumping out of liquid in each evaporator so longas the compressor removes vapor at a substantially constant ratemeasured by volume while the expansion valve holds evaporator pressurewithin the desired operating limits. As in my United States Patent No.2,497,903, the lengths of the operating periods will be substantiallyconstant even when there is a marked change of evaporating pressureduring each cycle as such change of pressure follows a substantiallyconstant curve and the result is a substantially constant number ofturns of the pinwheel 324 ina given period of time when this time periodspreads over a main portion of an average ice-making period.

As noted above, the suction valves 318 and 378 are normally opened bygravity except when held closed by high side pressure, thus when anevaporator approaches the end of its pumping out period, the pressure inthat evaporator drops to only a few pounds p. s. i. greater than that ofthe still active evaporator and the valve drops byits own weight. Theseat area and weight of the valve may be calculated so that the valveopens at the desired pressure difference representing a pressure whichcorresponds to the desired amount of liquid refrigerant remaining in theevaporator which is now to become active. This does not mean thatpressure is a measure of p the percentage of liquid refrigerant in acontainer but it will be found that with a compressor of a givendisplacement the inactive evaporator will retain a substantiallyconstant amount of liquid refrigerant at the time when its presssuredrops to a given point.

Any desired gear ratio may be used between the pinwheel 324 and the cam348 to provide a desired length of operating cycle for a given densityand rate of flow for suction vapor. It is not necessary to change thegear ratio to adapt this valve mechanism to a compressor of slightlydiiterent displacement per minute or for use at a different suctionpressure. Wide changes can be made in the speed of pinwheel 324 bytwisting its vanes or substituting a pinwheel having vanes of differentpitch or form. In selecting a pinwheel or adjusting vanes for a specificmachine, it is preferred to adjust for a shorter cycle than desired andthen make further adjustment during operation by means of the bypassvalve 386, so that more less of the refrigerant vapor flows from thechamber 320 to the suction line 274 without passing through the ports322. If the bypass valve 386 is tightly closed the valve mechanism willbe operated at its shortest cycle for a given density and rate of fiowof suction vapor. In such case the valve 386 may be opened occasionallyto drain oil from the chamber 320 if this chamber is not so arranged soas to drain oil through the ports 322 to the suction tube 274. Byselecting a pinwheel and gear ratio to provide a very short cycle it ispossible to produce very thin ice which crushes easily. To make thickerpieces of ice or prolong the freezing period so that two pieces join tomake still thicker disks it is then only necessary to open the bypassvalve to the extent required to effect the desired lengthening of thecycle.

In Figures 1 and 2 the valves 318 and 378 are mechanically actuated inat least their closing direction, but as explained later in connectionwith Figs. 4, 8 and 9, the valves controlling suction ports may beactuated by fluid pressure, making it unnecessary to provide mechanicalmeans to actuate the suction valves. This is particularly desirablewhere three or more evaporators are incorporated in one ice maker.Figure 3 illustrates a modification of Fig. l to fit a system such asshown by Fig. 8, but having five evaporators instead of three.

In Figure 3 the valve member 390 may be driven directly by the gear 346through shaft 342 which is connected with 390 at its closed end. Theradial hole or holes 392 receive liquid refrigerant from the bore 394which is open to a chamber supplied with liquid through tube 282 as ischamber 368 in Figure l. The valve member 390 is preferably tapered anddriven from its smaller end so that the high pressure liquid refrigerantentering its bore 394 holds 390 tightly seated in the'boss 396 which isa part of the housing enclosing the gear train and the pinwheel 324. Thevalves and cam-actuated mechanism of Fig. 1 are omitted and there needbe but one inlet port for suction vapor so located as to drive the wheel324. Any leakage past the rotary valve member 390 goes into the gearhousing which forms part of the main suction passage, hence norefrigerant is lost. The radial ports in 396 and tubes connectedtherewith lead to valves which will be described later in connectionwith Figures 8 and 9.

Figure 4 shows another valve mechanism adapted for use in place of thevalve mechanism of Figure 1. Liquid refrigerant flows through the tube282, enters the chamber 402 and passes the open valve 404 to flowthrough the tube 406 into the chamber 408 from which it can exit onlythrough the tube 285 leading to the inactive evaporator 214 (Fig. 2).After passing from the inactive (defrosting) evaporator through theexpansion valve, as indicated by arrows in Fig. 2, this liquidrefrigerant evaporates in the active evaporator 216 and returns throughthe tube 270 to the chamber 410. Due to the fact that there ishighpressure liquid refrigerant in the chamber 408'*holding' the valve 412closed the valve "414 is held open-because'of thesetwo valves beingrigidly connected by the rod 416. The refrigerant vapor cannot flo'wthrough the tube 420 because the valve 422 is closedand held-so by thehigher pressure of liquid refrigerant within the chamber 402. Suctionvapor after passing the valve 414 into chamber 424 exits through 'themain suction tube274.

This operation continues while ice is being frozen by one evaporator andice is being released from surfaces associated with the otherevaporator. Inorder to'shift refrigerant flowso as to'release the icefOr'med-by-the one evaporator and start freezing'ice'on surfacesassociated with the other evaporator the magnet 426 -is moved first tothe-position 426 and after a short interval tothe'position 426". Insideof the casing 428, which is preferably made of brass or othernon-magnetic metal, the armature 430, which is pivoted at 432,follows'the movement of the magnet carrying with it the rocker 434 andthe valves 404 and 422. Movement of the magnet to the position 426allows'the valve 404'to close while'the valve 422 remains closed. Inthis position there is no flow of liquid refrigerant to either of theevaporators and refrigeration continues in the evaporator associatedwith tube 270 while liquid flows to it from the idle evaporatorconnected with tube 285.

This pumping out portion of the cycle is timed or otherwise controlledto terminate when the "amount of liquid refrigerant remaining inevaporator associated with tube 285, which has just finished itsice-releasing period, is'proper'for the start of refrigerationin it. Atthis time the magnet is moved from the position 426' to the'position426", thereby opening the valve 422 while valve 404 remains closed. Thisallows the high pressure liquid refrigerant in the chamber 402 to flowthrough the tube 420 with such force that the fluted end 436 of the rod416'is moved to the right causing valve 414 to close and valve 412 toopen. The restriction at this fluted portion of the rod, shown insection in Fig. 5,is considerable with respect to the high 'rate ofliquid flow at the instant-of opening of valve 422 but is not sufiicientto interfere with the normal rate'of flow maintainedduring an ice-makingperiod. The flutes 436 will naturally stop short of valve 412 and 414hence the liquid passage is nearly closed when the valve is'open. Wenow' have'high'pressure liquid refrigerant within the chamber 410holding the valve 414 tightly closed against its seat 438 while valve412 is securely held away frorn'its seat 440.

Refrigerant flow after reversal as above described is from the tube 282past the open valve 422 through the tube 420 to tube 270 and throughthe-evaporator with which it connects,'which is thereby heated, to theexpans'ion valve, from which it flows at reduced pressure intothe'evaporator which is now active, returning through the tube "285 tothe chamber 408, from which it "can only flow past the valve 412 becauseof valve 404 being closed. Suction vapor now flows'throughthe chamber424 to the main suction tube 274 which leads back to the "compressor. Atthe end of this ice-making period-the magnet 426 is moved from theposition 426 to the position 426' and then back to the original position426, which brings us back to the starting point. The -magnet 426 ispivoted externally of 402 on extensions'of the pivot 432 and-maybe'moved manually or by means of a suitable'rne'chanis m connected withthe pm 442. I

Figure 6 represents a solenoid valve which may be used in place of theliquid valve assembly shown in the upper portion of Figure 4. Such asolenoid valve lacks the feature of closing both liquid passages for'thepumping out period, hence it is preferred to substitute twosingle-acting solenoid valves as shown in Figure 7, where'the valve 452corresponds to valve 422 and valve 454 corresponds to valve 404.Suitable switch-mechanism actuated thermostatically, by'pressure changesor by clock means may be used to .produc'e'the-same efi'ects as theabove-described movements of'themagnet 426. Any required number ofsolenoid valves, one for each ice-maker evaporator, may be manifoldedtogether as in Fig. 7 to control systems such as seen in Figure 8.

Thus far I have described the use of my valve mechanism in connectionwith systems having two evaporators with 'only one evaporatoractive mostof the time, but in largersystems it is desirable to employ severalevaporators, each associated with an ice-making tank. This allowsseveral evaporators to be active in making ice while a smaller number,usually only one, is heated to releaseice. Such an arrangement is shownin Figure 8. Two of the three evaporators 460,462 and 464 are activein-freezing ice while the third one is heated by high pressure liquidrefrigerant for'thepurpose of releasing ice. In Figure 8 the'arrowsindicate refrigerant flow, showing liquid entering the manifold 466 fromtube 282. Since valves 470 and 472 are closed this liquid can only flowthrough the valve 474 and thence only through the valve 476 into theevaporator-coil 462. The valves 474 and 476 are seen in Fig. 9 inenlarged section in their'respec tive positions as required for flow astraced above. At this time a similar view of valves 470 and 478 or ofvalves 472 and 480 would differ as follows:

Solenoid 482 would not be energized, thus allowing valve 484 to closeand stopping flow of liquid to the valve assembly 476, 478 or 480, asthe case may be. This reduces the pressure in chamber 488, thus allowingthe valve 490 to drop so that the orresponding evaporator 460, 462 or464 is connected with the suction manifold 492 and thereby to thernainsuctiontube 274, which leads to the compressor 275. High pressurerefrigerant vapor'flows from the compressor into condenser 277 andliquidcondensed therein collects in receiver 278 to feed tube 282. p v 7Considering Figure 9 as applied to the evaporator 462 near the end ofits ice-releasingperiod, when the solenoid 482 is deenergi zed, itscircuit being broken by 'suitable control means 483 responsive to therelease of ice, to a temperature'rise or to the lapse of ample time forice to have released, the valve 484 will close. The liquid refrigerantwithinev-ap-orator 462 continues to feedevaporators 460 and 464 throughtheir respective expansion valves 4 96 until such time as the pressurewithin the evaporator 462 falls to nearly the operating pressuremaintained within the manifold 492. At thispoint thereis very littlepressure difierence across the valve 490 and therefore it will open dueto its own weight, whereupon flow will be reversed in the evaporator 462and vapor will now therefrom into the header 492 and thence to thesuction tube 274. Simultaneously liquid will flow from the manifold 494through the expansion valve 496 of evaporator 462 causing it to resumerefrigeration and thereby the formation of ice. We now have all threeevaporators actively cooled, but soon'one of the other evaporators 460or 464 will start the ice-releasing portion of its cycle in response toclosing of the switch which energizes the solenoid 482 of its liquid'valve 470 or 472. In case much time elapses between successivedefrostings the header 494 is enlarged to store liquid, but in largermultiples the defrostings overlap. I

Referring back to Fig. 3, this one valve, driven by the gear train andpinwheel of Fig, 1, may be used in place of five solenoid valves such as470, 472, and 474 of Fig. 8 and 4740f Fig. 9. It delivers high pressureliquid refrigerant to one or more of five tubes 486 at a time. Each tube486 leads to-a valve assembly 476 as in Figure 9. This would serve fiveevaporators'in place of the three seenin Figure8. It is possible to usethis arrangement of valves for any number of ice-making evaporators,eitherdriving the valvemember orrnembers 390 (Fig. '3') with-'ener-gyderived from vapor =flow" or by other means.

7 In connection with this arrangement attention is called to the factthat when one evaporator is 'being defrosted and say three evaporatorsare active all of the liquid refrigerant for theactive evaporators isflowing through the one being defrosted, hence it causes ice to releasein much less idle time.

An optional method of actuating the valve 390 or a switch to controlvalves 484 is to rotate the valve or a rotary switch by means of aratchet device and a bellows responsive to temperature changes on theorder of disclosures in my United States Patent No. 2,145,777 issuedJanuary 31, 1939. Such a bellows would be connected with a number ofbulbs corresponding to the number of evaporators in the ice maker. Thecharge of volatile fluid would be such that all but the warmest bulb arefilled with liquid. Each bulb is located adjacent to an ice-making areaassociated with one of the evaporators, preferably the last area fromwhich ice is released. As this bulb is warmed up to a temperature whichassures that all ice has been released from the surfaces served by thatevaporator the ratchet wheel is moved to its next position, shifting thevalve 390 to its next position to cause high pressure liquid refrigerantto flow into the next evaporator to release its ice.

The rotary valve of Fig. 3 is preferably so designed that only oneevaporator is flooded with hot liquid refrigerant at one time, though itis permissible to have these defrostingperiods overlap to some extent sothat two evaporators are defrosting simultaneously during short periods.When a single ice maker of large capacity is equipped with moreevaporators than can be handled by defrosting them one at a time and itbecomes necessary to have several of them defrosting simultaneously thecontrol may be made responsive to only a part of the evaporators and bearranged to shift two or more of them at a time. Another way to arrangethe control of such a large machine is to connect two or moreevaporators in parallel to each of the valves 476 (at tube 462 of Fig.9) thus the two or more evaporators so connected will be defrostedsimultaneously. Each solenoid 482 can be controlled by one evaporator ofsaid two or more, or ifthe valve of Fig. 3 is used the number of radialoutlets need only be equal to the number of valves 476.

While Figure 8 shows three expansion valves 496, it will be understoodthat a single expansion valve will serve with the addition of one morecheck valve for each evaporator on the order of my disclosure in UnitedStates ap plication Serial No. 109,942, new Patent No. 2,672,017, filedAugust 12,, 1949 and Fig. 4 of my U. S. application Serial No. 174,944.In this case each evaporator 460, 462, and 464 would have the outlet ofthe expansion valve leading to it through a check valve and the inlet ofthe expansion valve connected with three check valves, such as 498 ofFigure 8, one allowing flow from the same end of each evaporator to theinlet of the expansion valve. The opposite end of each evaporator wouldconnect with a valve 476, as in Fig. 8.

I claim:

1. In an automatic ice maker, a plurality of evaporators, means forminga suction passage for flow of refrigerant vapor from said evaporators,rotary means actuated by the flow of said vapor for controlling flow ofrefrigerant liquid to said evaporators, and means for controlling flowof refrigerant vapor from said evaporators, the said two means beingmechanically intercon nected to effect the stoppage of liquid flow toone of said evaporators prior to the start of vapor flow from saidevaporator, thus causing the liquid content of said evaporator to bereduced prior to the start of its next period of active operation as anevaporator.

2. In a refrigerating system, having a main suction conduit and a mainliquid conduit, a plurality of heat exchangers each arranged to serve atone time to evaporate refrigerant at low pressure and at another time asa heating device heated by high pressure refrigerant, means formodifying the path of refrigerant flow in said system to cause said heatexchanger to shift from one to the other of said functions, the lastsaid means including power actuated valve means for stopping the flow ofhigh pressure refrigerant to one of said heat exchangers which is beingheated while allowing refrigerant liquid to continue flowing from it toevaporate in another evaporator, and additional valve means actuated inresponse to a drop of pressure in said one heat exchanger to open itsoutlet to said suction conduit at a predetermined difference of pressurebetween said one heat exchanger and said suction conduit, thus causingthe heat exchanger to start functioning as an evaporator.

3. In a refrigerating system, an evaporator having an outlet forrefrigerant vapor, a suction conduit connected with said outlet, a highpressure refrigerant conduit, valve means controlling flow ofrefrigerant from said high pressure conduit to said outlet, and valvemeans for stopping refrigerant flow from said outlet to said suctionconduit, the last said valve means being closablc by flow of highpressure refrigerant caused by the opening of the first said valvemeans, and remaining closed until after the liquid content of theevaporator has been substantially reduced whereupon it opens.

4. In an ice-making system, a plurality of cvaporators, means fordefrosting one of said evaporator-s by flowing high pressure liquidrefrigerant through it to be expanded in an active evaporator, means forstopping flow of said liquid to the defrosting evaporator, and controlmeans for restarting the cooling of said defrosting evaporator as aresult of its liquid content and therefore its internal pressure beingreduced to a suitable, condition for such restarting.

5. In an automatic ice maker, a refrigerating system including aplurality of evaporators connected in parallel to the low pressure sideof said system, means for admitting high pressure liquid refrigerant toone of said evaporators at its normal outlet end, and valve meansresponsive to the admission of said liquid to stop flow from saidevaporator to the low pressure side of said system.

6. In a refrigerating system adapted to circulate a volatile refrigerantwithin itself, valve means including a plu rality of valves arranged tocontrol fluid flow between separate portions of said system and therebydivide the system into high and low pressure sections, a plurality ofevaporators of which any one may be connected in a high pressure or alow pressure section of the system according to which of said valves areclosed, a fluid-driven motor within said system arranged to be actuatedby refrigerant flow, and a power transmission mechanism connected withsaid motor to operate said valves in a sequence to first close a valvewhich stops flow of high pressure refrigerant to one of said evaporatorswhile refrigerant continues to flow from it to a low pressure section ofthe system and after a material reduction of the refrigerant content ofsaid evaporator to open another valve which allows flow of refrigerantvapor from said evaporator to a low pressure section of the system.

7. In a refrigerating system having high and low pressure sectionscharged with a volatile refrigerant, two or more evaporators, valvemeans for regulating the, flow of said refrigerant to cause one of saidevaporators to be defrosted by being filled with high pressurerefrigerant in its liquid phase while liquid refrigerant flows from itto an active evaporator, then to stop the flow of high pressurerefrigerant to said one evaporator while allowing liquid refrigerant tocontinue flowing therefrom into the low pressure section of said system,and then to open said one evaporator for vapor flow therefrom to the lowpressure section of said system after a considerable reduction in itsliquid content.

8. In a refrigerating system charged with a volatile refrigerant, anevaporator, means forming a chamber having three ports of which a firstone is connected with said evaporator, a suction conduit for vaporflowing from a second port of said chamber, a high pressure refrigerantconduit carrying liquid to the third port of said chamber, a valveadapted to close said second port, a valve controlling fiow from saidhigh pressure conduit to said evaporator for the purpose of defrostingit, and means actuated coincidentally with the starting of flow of highpressure refrigerant to said evaporator when the second said valve isopened to close the first said valve, said means also acting to closethe second said valve and to provide for the later re-opening of thefirst said valve whereby the evaporator is caused to resume normaloperation after being defrosted.

9. In a refrigerating system charged with a volatile refrigerant, anevaporator, a 3-way fitting having one port connected with the vaporoutlet of said evaporator, a

suction conduit leading from a second port of said fitting,

a high pressure refrigerant conduit connected with the third port ofsaid fitting, a valve adapted to close said second port, a Valve in saidhigh pressure conduit, means actuated in time with the flow of highpressure refrigerant to said evaporator when the second said valve isopened to close the first said valve, a second evaporator in said systemarranged to be fed with liquid refrigerant from the first saidevaporator while the first said evaporator contains high pressurerefrigerant, and means acting to hold the first said valve closed untilflow of liquid from the first said evaporator has reduced its liquidcontent and pressure to a point suitable for resumption of its operation,as an evaporator.

10. In a refrigerating system employing a volatile refrigerant, aplurality of evaporators, means forming a suction passage leading from afirst one of said evaporators, a check valve located between said firstevaporator and its suction passage, said check valve being closable bymovement in the normal direction of flow from said first evaporator tosaid suction passage and biased in its opening direction during at leastthe active periods of said first evaporator, means for defrosting saidevaporator by filling it with refrigerant at a higher pressure thanusual and coincidentally closing said check valve, and control means forregulating the flow of said higher pressure refrigerant to a second oneof said evaporators for evaporation therein while fiow of refrigerant tothe first evaporator is stopped, thereby bringing the refrigerantcontent of the first evaporator down to a normal quantity and reducingits pressure so that said check valve reopens to resume cooling of thefirst evaporator.

References Cited in the file of this patent UNITED STATES PATENTS1,976,204 Voorhees Oct. 9, 1934 2,145,774 Mufily Jan. 31, 1 9392,359,780 Mufily Oct. 10, 1940 2,368,675 Mufiiy Feb. 6, 1945 2,407,794Mufily Sept. 17, 1946 2,444,514 Kubaugh July 6, 1948 2,448,454 MnfiiyAug. 31, 1948 2,486,608 MacDougall Nov. 1, 1949 2,497,903 Mufliy Feb.21, 1950 2,542,892 Bayston Feb. 20, 1951 2,590,499 Braswell Mar. 25,1952 2,654,227 Muffiy Oct. 6, 1953 2,672,016 Mufily Mar. 16, 19542,672,017 Mufily Mar. 16, 1954

